Angel Granados-Diaz was 18 when he brought the gun to school on May 17.
The video — obtained Friday from the Multnomah County District Attorney's Office through a public records request — is the visual accompaniment to the story recounted by Lowe during a press conference earlier this year.
The Multnomah County District Attorney's Office said Granados-Diaz brought the gun, which was loaded with one round, to the school grounds during a mental health crisis.
Officials said he never pointed the gun at anyone other than himself. Investigators said he made suicidal statements to another person before bringing the gun on campus.
A Multnomah County court handed down a 36-month probation sentence under a pretrial agreement for one count of unlawful possession of a firearm in a public building and one count of unlawful possession of a loaded firearm in public.